In the field of power integrated circuits much work has been done in the development of power transistors. Advancements were made enabling LDMOS power transistors (lateral double diffused MOS transistor) to exhibit low "on-resistance" (RDSon) and high breakdown capability concurrently through a reduced surface field (RESURF) technique (J. A. Appels and H. M. J. Vaes, "High Voltage Thin Layer Devices (RESURF Devices)", IEDM Tech. Digest, pp. 238-241, 1979).
In the past, RESURF LDMOS transistors commonly were used in low side driver applications because the transistor structure coupled the source to the substrate which in turn was coupled to ground. (A low side driver configuration consists of the source of the LDMOS transistor coupled to ground and the drain coupled to an output load.) Therefore, RESURF LDMOS transistors were not utilized in high side driver applications and other applications that mandated electrical isolation between the source and substrate. (A high side driver configuration consists of the LDMOS transistor drain coupled to circuitry or a power supply and the source coupled to an output load.)
It is an object of this invention to provide a high power integrated circuit device with electrical isolation between source and substrate. It is another object of this invention to provide a LDMOS transistor with an isolated source and RESURF drift region. Other objects and advantages of the invention will become apparent to those of ordinary skill in the art having reference to the following specification together with the drawings herein.